In the manufacture of integrated circuits, interconnects are used to couple active and passive devices together and to couple together conductive lines formed on different layers of the integrated circuits. To keep the resistivity in the interconnects low, interconnects are generally fabricated from good conductors, such as aluminum, copper, or alloys of aluminum or copper. Keeping the resistivity of the interconnects low decreases the heat generated in the interconnects, which permits the fabrication of higher density circuits.
Unfortunately, even for interconnects having a low resistivity, the interface between the interconnect and an active or passive device or the interface between the interconnect and a conductive line may have a high resistivity. High resistivity at an interconnect interface is often caused by an unclean surface at the interface. Preclean procedures and preclean chemicals, such as phosphoric acid, and hydrofluoric acid, are used to prepare semiconductor surfaces at interconnect interface sites. Unfortunately, these chemicals contain strong (i.e., concentrated and not dilute) organic solvents, which require special hazardous waste disposal techniques.
For example, U.S. patent application Ser. No. 08/808,014 (which is assigned to the same assignee of the present invention) discloses suitable compositions useful as cleaning compositions in integrated circuits semiconductor fabrication. The compositions include water, phosphoric acid, and acetic acid. The compositions are successful in reducing surface aluminum fluorides but require special hazardous waste disposal techniques. Preclean procedures and chemicals are also used to prepare metal surfaces, such as aluminum or copper surfaces, at interconnect interface sites. Unfortunately, the common contaminants, such as residual organic and metallic impurities are difficult to remove, and the conventional cleaning compositions also require special hazardous waste disposal techniques.
For these and other reasons there is a need for the present invention.